Due to high current density, high breakdown voltage, and low ON resistance, High Electron Mobility Transistors (HEMTs) are suitable for use in power applications. An HEMT structure includes a channel layer and an active layer. A two-dimensional electron gas (2DEG) is generated in the channel layer, adjacent an interface with the active layer. The 2DEG is used in the HEMT structure as charge carriers. A consideration in designing HEMT structures involves breakdown voltage improvements. A breakdown voltage of an HEMT structure is a gate voltage at which the drain current sharply increases. A high breakdown voltage indicates the ability of the HEMT structure to withstand a high gate voltage without being damaged and/or exhibiting irregular current behaviors.